1. Field of the Invention
The invention relates to a power layout design of an integrated circuit (IC), and more particularly, to a layout design of a power mesh and a power ring in an integrated circuit.
2. Description of the Prior Art
Please refer to FIG. 1A. FIG. 1A shows a simplified sectional view of a conventional IC die (or a chip) 1. As shown in FIG. 1A, the IC die 1 includes a semiconductor layer 10, six successive metal layers (121˜126) from bottom to top, several insulating layers 14 formed between two adjacent metal layers respectively, and a passivation layer 16. The semiconductor layer 10 is used for forming electronic components such as transistors (not shown in FIG. 1A) and electrical routing among these electronic components. In order to achieve the minimal chip area and the fastest circuit rate, generally, only shorter electrical connections are formed on the semiconductor layer 10. The metal layers 121˜126 are provided for other electrical connections. The number of the metal layers is determined by the complication of the practical routing. For example, eight or even more metal layers are widely used for IC design with complicated routing.
Regarding the routing at the metal layers 121˜126, a power distribution network (not shown in FIG. 1A) can be formed at the first metal layer 121 and coupled to the electronic components. The power distribution network may be made of metal rails with finer line widths.
Please refer to FIG. 1B. FIG. 1B shows the higher metal layers of the IC die 1 and the routing formed thereon.
As shown in FIG. 1B, a power mesh 18 is formed at the sixth metal layer 126 and the fifth metal layer 125. The power mesh 18 includes metal trunks 182 and 184 with line widths wider than the metal rail. In addition, the metal trunks 182 and 184 formed at different metal layers 125 and 126 are interconnected by a via 142 formed at the insulating layer 14. In the same way, the power mesh 18 is connected to the power distribution network by the via 142. The metal trunks 182 and 184 are divided into a power metal trunk 182 for connecting power and a ground metal trunk 184 for connecting ground. At the same metal layer, the power metal trunk 182 and the ground metal trunk 184 are interlaced. The metal trunks 182 and 184 formed at the sixth metal layer 126 are perpendicular to those formed at the fifth metal layer 125. The metal trunks 182 formed at the sixth metal layer 126 are only connected to the metal trunks 182 formed at the fifth metal layer 125, and the metal trunks 184 formed at the sixth metal layer 126 are only connected to the metal trunks 184 formed at the fifth metal layer 125.
Please refer to FIG. 1B again. A power supply ring 17 (a small section of the power supply ring 17 is shown in FIG. 1B) can be formed at the sixth metal layer 126. In practical applications, the power supply ring 17 consists of two metal rings 172 and 174 with line widths larger than the metal trunk 182 and 184. The two metal rings 172 and 174 are divided into a power metal ring 172 for connecting power and a ground metal ring 174 for connecting ground. The metal rings 172 and 174 are formed at the sixth metal layer 126, and the metal rings 172 and 174 surround the metal trunks 182 and 184 which are also formed at the sixth metal layer 126 to form a ring structure (not shown in FIG. 1B). The power supply ring 17 is used for receiving a power and conducting the power to the power distribution network through the power mesh 18. The power distribution network is used for distributing the power to the electronic components.
When designing an IC, in order to provide well-planned power structures, it is necessary to collect a variety of specifications to match various requirements of the manufacturing process, the yield, and the occupied resource. Because a lot of details are requested, the power structures must be planned and accomplished by experienced layout engineers. As a result, a huge human resource burden is induced.